Novel EGR2 variant that associates with Charcot-Marie-Tooth disease when combined with lipopolysaccharide-induced TNF-α factor T49M polymorphism.

OBJECTIVE: To identify novel genetic mechanisms causing Charcot-Marie-Tooth (CMT) disease. METHODS: We performed a next-generation sequencing study of 34 genes associated with CMT in a patient with peripheral neuropathy. RESULTS: We found a non-previously described mutation in EGR2 (p.P397H). P397H mutation is located within the loop that connects zinc fingers 2 and 3, a pivotal domain for the activity of this transcription factor. Using promoter activity luciferase assays, we found that this mutation promotes decreased transcriptional activity of EGR2. In this patient, we also found a previously described nonpathogenic polymorphism in lipopolysaccharide-induced TNF-α factor (LITAF) (p.T49M). We show that the p.T49M mutation decreases the steady-state levels of the LITAF protein in Schwann cells. Loss of function of LITAF has been shown to produce deregulation in the NRG1-erbB signaling, a pivotal pathway for EGR2 expression by Schwann cells. Surprisingly, our segregation study demonstrates that p.P397H mutation in EGR2 is not sufficient to produce CMT disease. Most notably, only those patients expressing simultaneously the LITAF T49M polymorphism develop peripheral neuropathy. CONCLUSIONS: Our data support that the LITAF loss-of-function interferes with the expression of the transcriptional-deficient EGR2 P397H mutant hampering Schwann cell differentiation and suggest that in vivo both genes act in tandem to allow the proper development of myelin.

Frecuente alteración de la vía amiloide en la demencia con cuerpos de Lewy prodrómica / Frequent involvement of the amyloid pathway in prodromal dementia with Lewy bodis

Introducción. La demencia con cuerpos de Lewy (DCLW) es la más frecuente de las degenerativas, después de la enfermedad de Alzheimer. Objetivo. Analizar los biomarcadores core de la enfermedad de Alzheimer en el líquido cefalorraquídeo de pacientes exclusivamente hispanos con DCLW prodrómica, para conocer si existe alteración de la vía amiloide o de la vía tau. Pacientes y métodos. Entre 2008-2017 incluimos a 430 pacientes con deterioro cognitivo leve según los criterios de Petersen, procedentes de tres hospitales de la provincia de Alicante. Se les realizaron revisiones clínicas cada 6-12 meses para evaluar su estabilidad clínica o la progresión a demencia utilizando los criterios clínicos vigentes. Entre otras pruebas complementarias se analizaron los biomarcadores de enfermedad de Alzheimer en el líquido cefalorraquídeo. Resultados. Entre todos los pacientes incluidos, 26 desarrollaron DCLW y 29 se mantuvieron estables durante al menos cinco años, por lo que los consideramos como referencia. En este grupo solamente cinco (17%) tenían valores de proteína Abeta(1-42) inferiores a la normalidad, mientras que 16 (55%) de los pacientes con DCLW tenían niveles alterados. No se encontraron diferencias en los niveles de las proteínas tau. Al comparar los grupos con DCLW con y sin amiloidosis solamente encontramos diferencias en los niveles de proteína Abeta(1-42). Conclusiones. Destacamos la frecuente presencia de patología amiloidea en la DCLW prodrómica en nuestra población y la probable alteración de diferentes vías metabólicas en una misma demencia clínicamente definida

Introduction. Lewy body dementia (LBD) is the most frequent of the degenerative dementias, after Alzheimer’s disease. Aim. To analyse the core biomarkers of Alzheimer’s disease in the cerebrospinal fluid of exclusively Hispanic patients with prodromal LBD, in order to determine whether there is involvement of the amyloid pathway or the tau pathway. Patients and methods. Between 2008 and 2017 we included 430 patients with mild cognitive impairment according to Petersen criteria, from three hospitals in the province of Alicante. They underwent clinical check-ups every 6-12 months to evaluate their clinical stability or their progression to dementia using current clinical criteria. Among other complementary tests, biomarkers for Alzheimer's disease in the cerebrospinal fluid were analysed. Results. Of all the patients included, 26 developed LBD and 29 remained stable for at least five years, and were thus considered as a reference. In this group only five (17%) had Aβ1-42 protein values below normal, whereas 16 (55%) of the patients with LBD had altered levels. No differences were found in the levels of tau protein. On comparing the LBD groups with and without amyloidosis, differences were only found in the levels of Aβ1-42 protein. Conclusions. We highlight the frequent presence of amyloid pathology in prodromal LBD in our population, and the probable involvement of different metabolic pathways in the same clinically defined dementia